One or more embodiments relate to a power semiconductor device with charge compensation structure and a method for producing the same.
A power semiconductor device is known from the document U.S. Pat. No. 5,216,275. The power semiconductor devices proposed therein have a drift path having drift zones and charge compensation zones, referred to as a composite buffer layer (CB layer). Such charge compensation devices having depletable complementarily doped charge compensation zones in the form of complementarily doped pillars have the disadvantage, in the case of very precise charge compensation and constant doping of the pillars over the depth thereof, that the reverse voltage falls significantly in the event of an alternation of the compensation as a result of current flow of a few amperes in the off-state case when the avalanche case occurs. The reverse characteristic curve, which is initially characterized by a reverse current determined by the intrinsic conduction of the semiconductor material, undergoes transition to the breakdown characteristic curve in the avalanche case and exhibits a “snapback effect” upon additional take-up of a voltage. The snapback effect is characterized by the fact that the reverse voltage decreases significantly even at low currents without the device being destroyed.
The snapback effect or the snapback of the breakdown characteristic curve can be stemmed in charge compensation devices by using a variable doping of the charge compensation zones, as is known from the document DE 198 40 032 C1. However, this solution can be applied only to a limited extent to a technology in which the charge compensation is produced by stacking selectively doped epitaxial layers. For techniques in which the charge compensation zones are effected by introducing trench structures in which the n-type or p-type doping is introduced via trench sidewalls, a variable doping of the charge compensation zones cannot readily be realized, however.
For these and other reasons, there is a need for the present invention.